At the 200th anniversary of the New Madrid earthquakes, all eyes are on this still active seismic zone in the nation's midsection

By Elisabeth Boone, CPCU

In the lore of U.S. earthquakes, most people think of The Big One as the Great San Francisco quake of 1906, which registered an estimated 8.0 on the Richter scale.

More than 3,000 people perished as the ground opened under their feet, buildings collapsed like dominoes, and ruptured gas lines spawned a conflagration that destroyed much of the city.

The San Andreas Fault that triggered the San Francisco earthquake runs the length of California and has spawned countless temblors, including the Loma Prieta quake (magnitude 6.9) that resulted in more than 60 deaths and the 1994 Northridge quake that measured 6.7 and killed some 60 people.

The Loma Prieta temblor is described by the U.S. Geological Survey (USGS) as "a wakeup call to prepare for the potentially even more devastating shocks that are inevitable in the future" in the San Francisco Bay region. Early detection and warning systems are a key focus of scientists' efforts because the fault runs through a heavily populated area of California, and early alerts can save lives.

Seismologists, geologists, and meteorologists are acutely aware of the massive forces that can be released by the shifting of the huge tectonic plates along the faults that criss-cross the country.

Last year's earthquakes in Virginia (5.8) and Oklahoma (5.6) likewise spurred seismologists to intensify their study of activity along the respective faults that spawned those highly unusual quakes. Around the world, awareness is at an all-time high because of what seems to be a global "epidemic" of earthquakes: Japan (2011), Haiti (2010), New Zealand (2011), and the countries that border the Indian Ocean (2004).

The "big one" in the heartland

For decades—in fact, for centuries—scientists have had their eyes and their instruments trained on the New Madrid Fault, a seismic zone in the central Mississippi Valley that in 1811 and 1812 produced a series of three temblors of such magnitude that the course of the mighty Mississippi River was temporarily reversed and the water began to flow north. The quakes generated thousands of aftershocks that lasted for several years.

In a February 2012 report titled "Earthquakes: Risk and Insurance Issues," the Insurance Information Institute notes that the New Madrid quakes, whose estimated magnitudes were 8.0 or greater, were the largest in the continental United States. (The largest U.S. earthquake was the 9.2 temblor that struck Alaska in 1964.)

According to the report: "Earthquakes in the central and eastern United States affect much larger areas than earthquakes of similar magnitude in the West. For example, the San Francisco earthquake of 1906 was felt 350 miles away, whereas the New Madrid earthquake of December 1811 rang church bells in Boston, Massachusetts, 1,000 miles away."

The New Madrid Fault (New Madrid, Missouri, is believed to have been the quakes' epicenter) encompasses an area from St. Louis, Missouri, to Memphis, Tennessee, and the record of its geologic history suggests that the fault has triggered earthquakes of 7 to 8 magnitude for thousands of years. Both the record and recent activity suggest that the New Madrid Fault is a highly active seismic zone that remains capable of triggering major earthquakes, with the potential for damage and loss of life that did not exist 200 years ago when the earthquakes struck sparsely populated rural areas.

The inhabitants of the region weren't watching gas lines explode and tall buildings collapse into rubble, but they must have been terrified as they witnessed the savage forces of nature that turned their crop fields into swamps, covered roads with mud and sand, and rearranged the landscape by cutting new river channels and filling existing ones with rock and other debris. Although the loss of life was significantly less than it would be in the 1906 San Francisco quake, the USGS cites reports that many boaters were drowned as large waves overtook their craft.

FEMA (the Federal Emergency Management Agency) didn't come into existence until 1979, but the federal government did offer help to victims of the New Madrid earthquakes whose property had been destroyed. According to the USGS, in 1815 Congress passed the first disaster relief act, which provided the owners of ravaged land an equal amount of land in unaffected regions.

Anniversary = awareness

People who live in the New Madrid Fault zone are acutely aware of both its history and its potential to trigger devastating temblors. In recent years, in fact, quakes in the range of 3 to 4.5 magnitude have shaken people from sleep, damaged vehicles and building foundations, and caused mostly minor injuries. Once over their alarm, residents joked about what they thought was going on when the temblors struck, but they take such jolts as a solemn reminder of what has happened, and what could happen, in this highly volatile seismic zone.

"What could happen" could be catastrophic, according to estimates presented in a Munich Re report titled "The New Madrid Earthquakes of 1811-12."

Citing the three-temblor event and its thousands of aftershocks, the report says: "A repetition of a similar sequence today would cause . . . a serious disruption of vital infrastructure." The report continues: "The built environment in the central United States, including infrastructure, is far less resistant to earthquakes on average than in the more seismically active regions of the U.S., especially California."

Two hundred years ago, as noted earlier, the New Madrid Fault region was sparsely populated; and, although St. Louis and Memphis were key ports on the Mississippi River, they were not the major metropolitan areas they have since become. The Munich Re report contains some stark predictions about the likely impact of a future event of the magnitude of the 1811-1812 quakes.

"Today, more than 15 million people live in the area affected by the 1811-1812 earthquakes," the report says. "Putting the hazard and vulnerability elements together yields a direct economic loss potential in the three-digit billion-dollar range for a single high-magnitude earthquake." The report goes on to describe potential disruption of transport routes, energy distribution, and rescue and recovery operations.

In a sober reminder of the 2011 earthquake and tsunami that resulted in catastrophic loss of life and triggered deadly emissions at several Japanese nuclear power plants, the report says: "It should also be noted that 15 nuclear power plants are located within the New Madrid Seismic Zone."

Heeding the call

Earlier this year, the 200th anniversary of the New Madrid earthquakes garnered attention throughout the region as residents of nine states in the fault zoneparticipated in earthquake preparedness drills and other events designed to heighten awareness and teach residents how to protect themselves in the event of a quake. "The Great Central U.S. ShakeOut" is a partnership of the Central United States Earthquake Consortium, each participating state, FEMA, and other organizations.

The ShakeOut was held on February 7. In an eerie coincidence, just two weeks later, on February 21, a 4.0 earthquake centered near East Prairie in southeastern Missouri shook residents awake just before4 a.m. The quake was felt as far away as St. Louis, some 100 miles to the northwest, and eight other states in the New Madrid Fault zone also experienced some shaking. Damage was minor, but the temblor turned up the volume on the wakeup call that first sounded along the fault 200 years ago.